CHAPTER XYIII 



THE CLUSTER FLY POLLEXIA RUDIS FAB. AND MUSCINA 



STABULANS FALL. 



The first of these two species, Pollenia rudis, is common in 

 Europe and North America. On account of their habits and 

 general appearance they are usually mistaken by the uninitiated 

 for house-flies emerging from their winter sleep. Early in spring 

 and sometimes during mild days in winter they may be found 

 crawling sluggishly around, as is their habit. Out-of-doors one 

 may find them on the snow around buildings or on the walls. 

 In-doors they buzz lazily, firequently in considerable numbers, in 

 the windows and especially on the windows of unoccupied rooms. 

 I have found them out-of-doors on the snow at Ottawa as early as 

 the middle of March. In England I have observed them entering 

 the sun-lit window of a bed-room in a country house and swarm- 

 ing over the window panes. They appear to frequent especially 

 country houses covered with creepers and vines. The name 

 " Cluster-fly " has been given to them on account of their habit of 

 congregating in large numbers in and about houses and other 

 occupied buildings. They appear to prefer unoccupied rooms, no 

 doubt on account of the absence of disturbance. 



Howard (1911) refers to the observations of Dall in the United 

 States, which confirm my own made on the habits of this fly in 

 England and Canada. Dall states that this fly was a great 

 nuisance in country houses near Geneva, New York State, They 

 were a teri'or to housekeepers since they were found in all kinds 

 of places such as in and on beds, wardrobes, behind pictures, etc. 

 They would form large clusters about the ceilings of clean, dark 

 rooms seldom used. It was stated that about the first of April 



